This commit adds support for fetch-and-add and compare-and-swap when
using the mlx5 driver. The support is only enabled if the expanded
verbs interface is detected. This is required because mlx5 HCAs return
the atomic result in network byte order. This support may need to be
tweaked if Mellanox commits their changes into upstream verbs.
Closesopen-mpi/ompi#1077
Signed-off-by: Nathan Hjelm <hjelmn@lanl.gov>